The present invention relates to a light beam scanning apparatus and more particularly to an apparatus using a plurality of light sources for scanning a plurality of light beams in parallel.
In a conventional light beam scanning apparatus such as a laser beam printer, light beam scanning is effected by moving a rotating polygonal mirror or a vibrating mirror at a high speed. With such arrangement, to attain higher speed operation and improved resolution, it becomes necessary to increase the operating speed of the rotating polygonal mirror or the vibrating mirror a great deal. However, there is a limit in its attainable speed. To cope with such a situation, a light beam scanning apparatus using a plurality of light sources so that a plurality of light beams are scanned in parallel on a scanned plane, while the beam spacing is kept constant, is proposed in Japanese Laid-open Pat. No. 60-166916, for example.
Such a hitherto proposed apparatus, however, has been designed to keep the spacing between the scanning beams at a predetermined constant value at all times, and there has not been given any consideration to have the beam spacing suitably changed so that its recording (pixel) density may be changed. Therefore, it has been difficult to change the recording density of the printer to a desired value.